The midterm contest is almost over and the Republicans are winning. That, at least, is the impression left by some modelers and other analysts. But three months out from November, many questions remain before the ballots can be counted.

For politics aficionados, half a dozen outlets are offering assessments and predictions. Three use traditional methods of handicapping (analysis of polls and reporting): the Cook Political Report, the Rothenberg Political Report and Larry Sabato’s Crystal Ball. Three others employ modeling to develop probability assessments. They include Nate Silver’s FiveThirtyEight.com (the best known of the group), The Washington Post’s Monkey Cage and the New York Times’s Upshot.

In one form or another, all point toward a Republican takeover of the Senate, although their leanings vary significantly. The Monkey Cage is by far the most bullish, saying that it is more than 80 percent likely that the Republicans will take control of the Senate in January. Others suggest that the battle will continue to rage until November.

Republicans need to win a net of six seats to take the reins. Three states are considered almost certain to switch from Democrat to Republican: Montana, South Dakota and West Virginia. It’s relatively easy to assume they will gain one or two. The debate is about how many more Republicans will win beyond that. They have plenty of options but their victories must come either by defeating Democratic incumbents in red states or picking off seats in blue or purple states that Barack Obama and the Democrats have been winning in presidential elections.

To give some idea of the differences in current assessments of the outlook, the Upshot has published a chart summarizing what the six election forecasters say about 10 competitive Senate races (beyond Montana, South Dakota and West Virginia).

Election Lab: See our current forecast for every congressional race in 2014

The Cook report listed nine of the 10 as toss-ups. The Monkey Cage’s analysis listed only one as a toss-up. The Upshot modeling counts seven toss-ups. Silver and Rothenberg each say there are six (and agree on what they are), while Sabato’s analysis lists five as too close to call.

Republicans feel confident for several reasons. First and perhaps most important, key contests will be fought on turf favorable to the GOP. They could win control of the Senate without ever having to win a state Mitt Romney lost in 2012.

To do that means they will have to overcome one serious obstacle: They must defeat incumbent Democrats in Alaska, Arkansas, Louisiana and North Carolina. Their best chances appear to be in Arkansas and Louisiana. Alaska and North Carolina are more problematic.

At the beginning of the year, those four states were considered the prime battlegrounds, with Republicans needing to win in three of them to take control. Now, the map of competitive races has expanded. One Republican strategist noted in a recent e-mail that the GOP might have to win only two of those four Democratic-incumbent states because there are opportunities elsewhere.

Four states that Obama won in 2008 and 2012 are either highly competitive or could become competitive: Colorado, Iowa, Michigan and New Hampshire. The key for Democrats in November could be their ability to protect all four.

Colorado and Iowa are considered toss-ups by both parties. Iowa is an open seat being vacated by retiring Sen. Tom Harkin (D) and is now hotly contested because of stumbles by Democratic Rep. Bruce Braley and an impressive primary victory by Republican Joni Ernst. But that race has miles to go. In Colorado, Democratic Sen. Mark Udall faces a serious challenger in Republican Rep. Cory Gardner in one of the prototypical swing states. But Republicans still must oust the incumbent.

Neither Michigan nor New Hampshire is in the tossup category today, mainly because neither of the Republican candidates has proved to be as sure-footed as needed. If that changes, the outlook will darken for the Democrats.

Candidates vying for congressional seats in the 2014 midterm election were required to file a new round of campaign finance reports Tuesday, which record how much each candidate has raised this election cycle.

Then there is another ring of states that Obama won twice that Republicans talk about as potentially competitive, states such as Minnesota, Oregon and Virginia. Democratic incumbents in those states appear to be in decent shape. The reality is that if these states end up as truly competitive, the Republicans are no doubt looking at a bigger victory in November.

The Democrats have no illusions that they will be scratching until the end to retain control and that Vice President Biden might become the key to everything as the person who could break a tie in a 50-50 Senate next year. But they see the state of play from a different perspective.

Several factors give Democrats hope that they can minimize their losses. One is candidate quality. With some exceptions, they view their candidates as performing well and GOP challengers as weaker than expected. (Republicans agree that some of their challengers would do better if they were more aggressive in prosecuting the case against Obama and the Democrats.)

A second factor is that some of their most embattled incumbents, such as Sens. Kay Hagan (N.C.) and Mark Pryor (Ark.), already have sustained millions of dollars’ worth of negative ads this year. Democrats believe that there is not much new and negative that voters can be told about them and that the number of truly persuadable voters in these states is relatively low.

A third factor is the invisible ground game. Democrats say they are pouring more money into identifying, registering and turning out their voters than in any previous midterm election. One strategist predicted privately that what the Democrats are doing in one contested state will shock people. Still, no one will know until Election Day whether those claims about turning out voters — or Republican counterclaims that their ground game will be a major asset — are correct.

There are intangibles that will affect these races as well. The national mood, Obama’s standing with voters, local vs. national issues, enthusiasm on each side (currently favoring the Republicans), the effectiveness of candidates and campaigns, money and advertising.

That leaves Republicans in an enviable but not yet commanding position. They certainly can win control of the Senate, but over the next months they will have to earn it state by state by state.

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